Technical Field
The present invention relates to a plasma etching method for use in manufacturing a semiconductor device.
Background Art
The plasma etching apparatus used in processing of a semiconductor device generates ions and radicals by dissociating a reactive gas by plasma within a decompression chamber, and irradiates a surface of a sample with the ions and the radicals to process the sample. It is general to create energy for generating the plasma by electromagnetic waves. From the viewpoint of a method for inputting the electromagnetic wave, the plasma etching apparatus is roughly classified into two systems. One of the systems is an electrode discharge system such as parallel plate plasma or a magnetron RIE in which an antenna electrode for generating the electromagnetic wave is disposed in the decompression chamber. The other system is an electrodeless discharge system such as microwave plasma (for example, Japanese Patent Application Laid-Open Publication No. Hei-10-64881) or an inductively coupled plasma (for example, Japanese Patent Application Laid-Open Publication No. 2006-517743), in which the antenna electrode is disposed outside of the decompression chamber, and the electromagnetic wave is introduced through a dielectric window that separates the decompression chamber from the external. In a process (front end process) of forming a transistor among processes for manufacturing the semiconductor device, in order to prevent a temporal change in discharge characteristics due to the corrosion of the antenna electrode, or the deterioration of the transistor characteristic due to heavy metal released from the corroded antenna electrode, the electrodeless discharge system has been used. The electrodeless discharge system has such a feature that non-uniform plasma is generated on the decompression chamber side of the dielectric window. Accordingly, in order to uniformly etch a sample with a large diameter, there has been used a method in which the sample is sufficiently distanced from the dielectric window, and ions are uniformized by diffusion.